An internal combustion engine used for automobiles generally comprises a plurality of cylinders defined in an engine body which consists of a cylinder block and a cylinder head, an intake manifold or an intake air passage member provided on an intake side of the engine body defined on one side of the engine body with respect to a cylinder row direction, and an exhaust manifold or an exhaust air passage member provided on an exhaust side of the engine body with respect to the cylinder row direction.
In order to improve the exhaust gas performance, internal combustion engines which conduct exhaust gas recirculation (EGR) are provided with exhaust gas recirculating passage members for recirculating the exhaust gas from the exhaust side to the intake side.
As one example of the exhaust gas recirculating passage, there is a passage defined by an exhaust gas recirculating pipe (EGR pipe) disposed so as to pass beside a cylinder row end of the engine body or over the cylinder head cover, communicating the passage defined by the intake manifold with the passage defined by the exhaust manifold (for example, see Japanese patent application publication No. H8-218950). Another example of the exhaust gas recirculating passage is a passage with its main part being an internal passage passing through the cylinder head from the intake side to the exhaust side (for example, see Japanese patent application publication H11-82185).